Foam molded articles such as flexible polyurethane foams are used as a cushioning material for a product such as a vehicle seat. At the bottom portion of the foam molded articles, a reinforcing base fabric is arranged in order to enhance the rigidity of the urethane foam molded article as well as to prevent the leakage of urethane to the back side of the article. Examples of the reinforcing base fabric include a combination of a cheesecloth (victoria lawn) and slab urethane, and a coarse blanket. However, such reinforcing base fabrics are insufficient in improving the rigidity of the urethane foam molded articles, or insufficient for preventing the leakage of urethane to the back side, which are of a problem.
As a method of improving the above defects, there have been proposed various methods such as a method using, as a reinforcing base fabric, a nonwoven fabric in which a thin dense layer having a basis weight of 10 g/m2 to 30 g/m2 and a coarse bulky layer having a basis weight of 40 g/m2 to 100 g/m2 are integrated with each other (see, for example, Japanese Utility Model Application Publication (JP-Y) No. S62-26193), a method using a high basis weight nonwoven fabric having a basis weight of 110 g/m2 to 800 g/m2 and a fiber diameter of 1 d to 16 d (see, for example, Japanese Patent Application Laid-Open (JP-A) No. H2-258332), a method using a mehblown nonwoven fabric havinQ a fiber diameter of 10 μm or less as a dense layer (see, for example, JP-A No. 2004-353153), a method using a nonwoven fabric in which a web (a dense layer) formed of fibers having a fineness of 1.1 dtex to 2.7 dtex and a web (a bulky layer) formed of fibers having a fineness of 2.3 dtex to 8.8 dtex are provided by mechanically entangling (see, for example, JP-A No. 2007-146356), and a method using, as a reinforcing material for a foam molded article, a multilayer obtained by integrating a fibrous substrate layer such as a spunbonded nonwoven fabric and a staple fiber layer, provided on at least one side of the fibrous substrate layer, through the action of high-pressure water flow (see, for example, JP-A No. 2005-212204).
However, the reinforcing base fabrics for foam molding described in the above documents are all directed to solving problematic leakage during urethane foam formation and impregnation performance, and they are not materials which can reduce troublesome manual labor, such as cutting and sewing, before foam molding.
As vehicle seats become more advanced in design and involve more electronic components in recent years, the shapes of metal molds during urethane foam formation have become complicated. The need to conform to such complicated shapes causes a significant increase in labor in manually cutting and sewing the reinforcing base fabrics. As a method of saving the labor, there has been proposed a molding processing method in which a mold is covered with a nonwoven fabric sheet, and the nonwoven fabric sheet is then heated, spread, and compressed to conform to the shape of the mold, whereby processing before foam formation is easily performed. As an example of the reinforcing base fabrics used in this molding processing method, a nonwoven fabric sheet including a mixture of low-melting-point fibers and high-melting-point fibers is exemplified (see, for example, JP-A No. 2006-281768) Further, it has been proposed that a nonwoven fabric mainly composed of conjugate staple fibers including high and low melting components of polyester resin is used as an urethane reinforcing material to eliminate the need of cutting as well as to prevent the leakage of urethane during molding in the molding processing of urethane foams (see, for example, JP-A Nos. 2012-82548 and 2013-129950).
Further, there has been proposed to provide a dense layer to secure denseness (for example, JP-A No. 2013-129950). Furthermore, there has been proposed a multilayer nonwoven fabric for foam formation in which a reinforcing layer is provided on at least one side of a dense layer, and the dense layer is formed by providing a spunbonded nonwoven fabric layer on both sides of a meltblown nonwoven fabric layer and the meltblown nonwoven fabric layer and the spunbonded nonwoven fabric layer are partially thermocompression-bonded with each other (see, for example, WO 2012/008169). It is described that this multilayer nonwoven fabrics for foam formation have excellent resistance to the separation of layers, and even when the multilayer is provided (entangled) using a needle punch, surface powdering caused by fiber waste of the meltblown nonwoven fabric layer is reduced.